I was just ten when British troops first emerged onto the streets of Belfast and Derry, in a world that was then dominated by black and white television. To be honest, I don't remember a great deal of detail from those times, except that I saw my first (and only) "civilian" gunman in the Bogside area, in Derry, as my father and younger brother and I drove home from visiting family across the border in Donegal.

Deployment came right in the middle of four days of rioting, looting, shooting and burning in August 1969, and just after the Republic's Taoiseach, Jack Lynch, had moved Irish army hospital units to fields just outside Letterkenny - which we also passed on our way home that summer. By the end of those four days, eight people were dead and 750 injured.

Serious rioting began in the lower Falls area of Belfast with crowds of demonstrators targeting an RUC station (and a Protestant owned car dealership), apparently in support of residents in the Bogside. But it was to be the Catholic Falls that took the brunt of a Protestant backlash from the nearby Shankill Road. Within those few days, 1,505 Catholic families and 315 Protestant families fled their homes. A whole street, Bombay Street, was burned to the ground. A further 275 commercial premises were badly damaged or destroyed, of which 83% were Catholic.

Nearer to home, a "raiding party" came down from Belfast to search out Catholic-owned businesses in my home town for "special attention". They were politely but firmly turned away by Protestant regulars in my father's pub. But Northern Ireland was never to be quite the same again.

Whatever legitimate criticism of troop conduct and behaviour was made afterwards, one thing is clear: the troops didn't cause the initial descent into disorder. That came as part of what some might term the inevitable breakdown of relations between a deeply conservative and almost exclusively Protestant government (struggling between demands for universal suffrage and action against discrimination, and shrill, often apocalyptical, loyalism on the other) and a substantial, but increasingly disillusioned Catholic minority.

Paraphrasing Yeats, "things fell apart, the centre could not hold".

But if British troops didn't cause it, neither were they to pour balm on the situation. Their role that summer of simply setting themselves between Catholic communities and the police or loyalists brought them a large degree of local popularity. But it was a popularity that spectacularly disappeared the following year with a three-day military clamp down on the Falls that dispersed the last vein of public sympathy and turned much of West Belfast into a fertile recruiting ground for a newly constituted Provisional IRA.

As Fintan O'Toole notes, in today's Irish Times, from that time on, if not before:

Both militarily and ideologically, the army was a player, not a referee. As with the paramilitaries, most of the people it killed were civilians: of the 301 people who died at the hands of the British army, 121 were republican paramilitaries and 10 were loyalist paramilitaries. Just as deadly in its own way, though, was the extent to which the army's presence and actions actually supported the IRA's definition of the conflict.

It arrived with a colonial mentality, viewing Northern Ireland as another field for the operations it had run in Malaya, Kenya, Aden and Cyprus and identifying Catholics as the suspect population. (The army's assessment actually confirms what sounded like an apocryphal story that banners used in both Derry and Belfast to order rioters to disperse were written in Arabic.) This turned a complex, largely internecine conflict into an "anti-imperialist struggle" and it took the IRA 30 years to realise that it was fighting the wrong war.

As a family, we came out of the 30-year conflict relatively unscathed. It was like that for a lot of people. You learned to steer clear of trouble: keep your mouth shut, your head low, and pray that it would all come to an end soon.

But for people in communities like those around the Falls Road (rendered almost exclusively Catholic by the movement of nearly 4,000 families in the first few years of the conflict), the "cat and mouse" game between British Army and IRA became a way of life, if little understood or cared about by those outside those districts. It inflicted death and injury tolls that were proportionately much higher than for those enjoying relatively normal lives elsewhere. For them, the war with the British (and, at times, more often, with their Protestant neighbours) was at its most real. If it did not yield the absolute victory many hoped (and died) for, it produced a harder, more uncompromising, form of nationalist politics.

In 1969, few of us expected it would be "over by Christmas". But neither did we think it would go on long enough to shape our teenage and adult lives in quite the way that it did. In the end, the British Army has slowly left the streets, towns and villages of Northern Ireland, in calmer circumstances than those in which it arrived. The peace we feared we'd lost forever in the fearsome tumult of those early days has long since sneaked in through the backdoor, almost unnoticed.

It is with some relief that most of Northern Ireland's citizen's watch the British Army turn its attention elsewhere in the world. And with some hope that its political masters have learned some signal lessons. Alex Evans quotesMartin Van Creveld:

The most important insight of all, though, [came] over dinner in Geneva in 1995. My partner on that occasion was a British colonel, regiment of paratroopers, who had done several tours of duty in Northern Ireland. What he said can be summed up as follows: the struggle in Northern Ireland had cost the United Kingdom 3,000 casualties in dead alone. Of the 3,000, about 1,700 were civilians ... of the remaining, 1,000 were British soldiers. No more than 300 were terrorists, a ratio of three to one. Speaking very softly, he said: "And that is why we are still there."